1. Field of the Invention
The present invention relates to a modeling data creating system that creates data used by a layered modeling apparatus that forms a model by layering modeling layers, parts of which have been selectively shaped, on a base plane.
2. Description of the Related Art
With prostheses such as crowns, bridges, inlays, onlays, or implants used in prosthetic treatments for the purpose of restoring facial, masticatory, pronunciation, or vocalization functionality to patients, there is a demand for the devices to maintain a high degree of strength and durability within the oral cavity for a long period of time. In addition to restoring lost functionality, aesthetic qualities have also come into higher demand in recent years.
Conventionally-used manufacturing methods, which primarily involve manual work on the part of a dental technician, have been insufficient in meeting this increased demand. A high degree of expertise is required when manufacturing prostheses by hand. There is also a wide range of compatibility, functionality, and durability depending on the manual work performed. Furthermore, there is also the possibility for a large degree of variance even among prostheses created by the same worker. There has thus been significant instability with respect to quality.
In addition, when manufacturing prostheses, dental technicians must perform operations involving many steps while using an extremely wide variety of materials, and thus a wide range of materials, clinical knowledge, and extensive experience are necessary. Therefore, the dental technicians must endure long hours of work, which poses a significant burden to them. Furthermore, as a result of such conditions, the production costs of such prostheses have been climbing as well.
Meanwhile, various improvements are being made to materials to respond to the demand for increased physical properties, and new materials hitherto unused are coming into practical use. For example, porcelain fused to metal restoration, in which ceramics matching the color of natural teeth are baked onto the surface of a metallic frame, have conventionally been the mainstream. However, recent years have seen an increase in the manufacture of all-ceramic crowns in which the entire prosthesis, including the frame, is formed of ceramics, the manufacture of frames using aluminum, zirconia, or the like to provide a strength equal to or comparable to that of a metallic frame while also providing aesthetic qualities superior to metallic frames, and so on, with the goal of eliminating the metallic color from such frames.
Among these materials, items that are difficult to process by hand, whose manufacturing processes are extremely complicated or require long periods of time, or the like are not uncommon. The result is that the dental technician is required to have knowledge regarding these new materials, and have acquired or have experience with processing techniques, leading to an even larger burden.
In addition, procedures for correcting shrinkage of the prosthesis due to firing are more complicated than with conventional devices, and cases in which the manufacture of prostheses with a high compatibility is difficult are more common. This not only increases the burden on the dental technician, but also makes it difficult to satisfy the patient.
Prostheses manufactured in this manner, by a dental technician performing complicated and high-level procedures over a long span of time, thus have a limit in terms of output due to such manual manufacturing procedures. In light of an increase in demand for prosthesis due to recent trends toward an aging society and an increase in tooth loss due to periodontal diseases, it is currently difficult to maintain a sufficient supply of prostheses that have a certain level of quality.
In order to ameliorate such problems with conventional prosthesis manufacturing processes that rely mainly on manual work performed by a dental technician, many methods that attempt to improve the quality and increase the manufacturing efficiency of structural materials having complex structures by applying computer processing techniques, which have seen marked progress recently, have been developed.
For example, CAD/CAM cutout systems, which have been common in dentistry prior to the layered modeling method, use a method in which when manufacturing a frame by cutting a material with high physical properties, such as zirconia, a semi-sintered block material is first cut out and formed into shape before the final sintering. With this method, there is a significant loss of materials due to the occurrence of cut debris resulting from the cutting system. Moreover, in some cases, there are constraints on the shapes that can be processed; for example, an undercut shape cannot be processed.
However, correcting distortions caused by such shape constraints to maintain the compatibility ultimately requires the shape to be adjusted to the actual teeth, which involves long hours of manual labor. Also, because materials such as zirconia have high physical properties, they are difficult to cut with normal dental cutting tools, which makes it necessary to consume a large amount of cutting materials, leading to a rise in manufacturing costs. Furthermore, there have also been cases where the merits of production improvements and quality assurance resulting from mechanization, which solved problems with manual labor such as gaps in compatibility and finishing, were lost.
With a CAD/CAM cutout system that employs a method of cutting a block that has undergone a final sintering, the finishing operations are performed by a machine rather than a dental technician, meaning that the finish, compatibility, and so on tend to be stable, regardless of whether the level of the finish, compatibility, and so on is actually sufficient. However, in the case where, for example, zirconia is being cut, a high-physical property zirconia block is being cut from the first rough-cut step to the final finishing step, and thus the number of cutting tools that are consumed increases, as does the time for cutting. For this reason, the amount of energy consumed in order to run the device increases, resulting in an overall increase in the manufacturing cost.
In order to eliminate such problems with a dental CAD/CAM cutout system, a layered modeling apparatus that, for example, creates a desired model by layering a powder upon a modeling table in layers has been proposed (see, for example, Patent Documents 1 and 2).
FIG. 20 is a diagram illustrating a process by which the stated layered modeling apparatus forms a model. First, as shown in FIG. 20A, a powder is evenly distributed by a powder feeder 42 upon a modeling table 41 provided in the layered modeling apparatus, thereby forming a powder layer 51. Next, as shown in FIG. 20B, an inkjet head 43 ejects a solution onto an area 51a of the powder layer 51, the area 51a representing an area to be modeled. The area 51a, onto which the solution was ejected, is shaped by, for example, irradiation with light. The operations in FIGS. 20A and 20B are then repeated each time the modeling table 41 descends by a predetermined pitch. As a result, multiple powder layers, parts of each being selectively shaped, are layered upon one another, as shown in FIG. 20C. When the powder that has not been shaped is removed at the end, only the shaped portions remain as the model (see FIG. 20D). Using such a layered modeling apparatus makes it possible to form a structural material having a complex shape, such as a structural material used for dental purposes.
After this, the model is sintered and then run through a finishing process, thus completing the desired structure.                Patent Document 1: JP 2004-344623A        Patent Document 2: JP 2005-59477A        